This invention relates to an apparatus for accurately winding tubing into a coil of predetermined length having substantially flat ends and with the tubing wound helically in successive layers.
More specifically, the invention relates to a unique control system for level winding a coil in which the wound coil has the turns of all of its layers in closely adjacent relation to each other.
In the manufacture of tubing, such as copper tubing, the tubing is wound helically into multilayer reels or coils usually containing a predetermined length of the tubing. Prior attempts to form a very accurately wound helical pattern of tubing in each of the layers of the coil, especially where the winding is done at high speeds have not been successful because the traversing mechanism could not accurately level wind the tubing, especially where different diameters of tubing were to be wound at different times by the same traverse mechanism. While some types of mechanical traverse mechanisms will work acceptably for tubing of one diameter, they cannot accommodate different diameters. Previous traverse control mechanisms which do have variable-diameter capability become progressively less accurate as winding speed or line speed is increased.
The problems of inaccurate level winding are that excessive space between layers will allow tubing on the next layer to wedge between the turns on the lower layer. Hence, the tubing plastically deforms from its desired circular shape. Also, such wedging can lead to jerky behavior of the coil when subsequently being unwound into automatic fabrication machines.
Too little traverse will cause the tubing to "pile up" on the reel, thereby leading to kinking when a turn suddenly is bent over the small radius of an improperly laid lower turn.
Moreover, inaccurately wound coils are more vulnerable to damage from handling, as the turns do not have the maximum surrounding support from adjacent turns. They are also more vulnerable to unwanted deformation of some of the turns during subsequent annealing of the coil in a furnace.